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The 2013 U.S. GEOTRACES East Pacific Zonal Transect (EPZT) between Peru and Tahiti chosen to encompass a range of processes that influence the supply, removal, and internal cycling of trace metals in the ocean, including from east to west a productivity gradient, a large oxygen minimum zone, and the largest known hydrothermal plume. With respect to 236U and other anthropogenic radionuclides, the major source to the Eastern Tropical South Pacific has been global stratospheric fallout. In addition to this, nuclear tests conducted in the Pacific Ocean also generated tropospheric fallout. Here we present dissolved 236U profiles collected at 4 full-depth stations along the EPZT. After pre-concentration of 4L samples (LDEO) and purification (CNA), 236U was analyzed by AMS at one of two facilities depending on collection depth. Surface samples (first 400m depth) were analyzed at the 1MV CNA facility. In this case 236U /238U atom ratios were expected to be at the 1010 level, so the parameters of the CNA system were optimized to achieve the necessary abundance sensitivity. Deeper samples were measured at the 600kV ETH facility. The most relevant conclusions are the following. a) Concentrations of 236U range from 0.02x106 to 6.5x106 atoms/kg, showing a typical distribution associated to a conservative element for which the atmospheric input to the ocean dominates. b) Inventories of 236U range from 1.45x1012 to 2x1012 at/m2 , in agreement with the expected values for global fallout. c) Below 1000 m depth, the four profiles presented 236U / 238U atom ratios at the 1012 level, which are among the lowest ratios reported so far in seawater. d) A slight enhancement of 236U at the bottom layers, near the seafloor, might be detected and most especially close to the hydrothermal plume. e) No influence of the local fallout from the French Polynesia is observed. These results will be presented and discussed.

The 1 MV AMS system at the Centro Nacional de Aceleradores (CNA, Seville, Spain) was the first multielemental compact device designed and manufactured by High Voltage Engineering Europa (HVEE, Amersfoort, Netherlands). In February 2015, the stripper gas was changed from Ar to He. Since then, our group has worked extensively on the optimization of the new parameters of the measurement for actinides (236U, 237Np, 239,240Pu and 241,243Am). Besides, additional information on the stripping process with He gas at terminal voltages between 500 and 1000 kV has been gained. Maximum stripping yields for U3+ are achieved at about 650 kV, with a transmission through the accelerator of 38% (47% stripping yield). This is in contrast with Ar gas, with 11% maximum transmission for U3+ (16% stripping yield) [1]. Scattering processes with residual stripping gas along the highenergy acceleration tube, limit drastically the abundance sensitivity that can be actually achieved, on a system where only a sector magnet is available on the high-energy side. A thorough adjustment of the slits and of the stripper gas pressure becomes necessary to achieve competitive figures of merit for: a) 236U, being 9x1011 the lowest 236U /238U atom ratios that can be measured; and b) 237Np, where the 238U scattering tail imposes serious restrictions on the limit of detection. The experienced gained during these years on our system will be shared. On the other hand, the state of the art of the CNA actinides measurement program will be briefly presented.

A new multi-isotope plutonium standard for isotopic ratio measurements with Accelerator Mass Spectrometry (AMS) was created by gravimetric mixing of different single-isotope standards provided by IRMM (Pu-239, Pu-240, Pu-242, Pu-244). This standard material has been measured at the AMS facilities at Canberra (Australia), Cologne (Germany), Caserta (Italy), Sevilla (Spain) and Zurich (Switzerland). Additionally, the material was characterized using a Neptune MC-ICPMS (multi-collector inductively coupled plasma mass spectrometry) at the joint Cologne-Bonn isotope facility. The results of this laboratory intercomparison are presented and consensus values for the isotope compositions of the standard material are proposed.

In this work we present and evaluate a radiochemical procedure optimised for the analysis of U and Pu in seawater samples by Accelerator Mass Spectrometry (AMS). The method is based on Fe(OH) co-precipitation of actinides and uses TEVA® and UTEVA® extraction chromatography resins in a simplified way for the final U and Pu purification. In order to improve the performance of the method, the radiochemical yields are analysed in 1 to 10 L seawater volumes using alpha spectrometry (AS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Robust 80% plutonium recoveries are obtained; however, it is found that Fe(III) concentration in the precipitation solution and sample volume are the two critical and correlated parameters influencing the initial uranium extraction through Fe(OH) co-precipitation. Therefore, we propose an expression that optimises the sample volume and Fe(III) amounts according to both the U and Pu concentrations in the samples and the performance parameters of the AMS facility. The method is validated for the current setup of the 1 MV AMS system (CNA, Sevilla, Spain), where He gas is used as a stripper, by analysing a set of intercomparison seawater samples, together with the Laboratory of Ion Beam Physics (ETH, Zürich, Switzerland).

This study examined the 238Pu and 239+240Pu activity concentration and the 240Pu/239Pu atomic ratio in peat bogs sampled in 2012 from marshlands in central Madagascar. The purpose was to investigate the presence of plutonium isotopes, 238, 239, 240Pu, from the 1964 satellite failure carrying a SNAP-9A radiothermal generator. With an average 238Pu/239+240Pu activity ratio of 0.165 ± 0.02 (decay corrected to 1964), the peat bogs in Madagascar exhibit similar values as the ones found in the southeastern African continent, except they are one order of magnitude higher than expected (0.025) from global fallout in the Southern Hemisphere. The 240Pu/239Pu atomic ratio showed a distinct decrease for layers dating back to the mid-1960s (down to 0.069 compared with an anticipated ratio of 0.17 for global fallout), indicating that the SNAP-9A failure also resulted in an elevated deposition of 239Pu. The obtained results demonstrate that further Pu analysis in Madagascar and in southeastern continental Africa is necessary to fully account for the regional Pu deposition from the SNAP-9A event.

Characterization of atmospheric aerosols collected in Monaco (2004–2008) and in sediment traps at 200 m and 1000 m water depths at the DYFAMED (Dynamics of Atmospheric Fluxes in the Mediterranean Sea) station (2004) was carried out to improve our understanding of the impact of Saharan dust on ground-level air and on the water column. Activity concentrations of natural (Pb, Po, uranium and radium isotopes) and anthropogenic (Cs, Pu, Pu, and Pu) radionuclides and their isotopic ratios confirmed a Saharan impact on the investigated samples. In association with a large particulate matter deposition event in Monaco on 20 February 2004, the Cs (∼40 Bq kg) and Pu (∼1 Bq kg) activities were almost a factor of two higher than other Saharan deposition dust events. This single-day particle flux represented 72% of the annual atmospheric deposition in Monaco. The annual deposition of Saharan dust on the sea was 232–407 mBq m for Cs and 6.8–9.8 mBq m for Pu and contributed significantly (28–37% for Cs and 34–45% for Pu) to the total annual atmospheric input to the northwest Mediterranean Sea. The Cs/Pu activity ratios in dust samples collected during different Saharan dust events confirmed their global fallout origin or mixing with local re-suspended soil particles. In the sediment trap samples the Cs activity varied by a factor of two, while the Pu activity was constant, confirming the different behaviors of Cs (dissolved) and Pu (particle reactive) in the water column. The Cs and Pu activities of sinking particles during the period of the highest mass flux collected in 20 February 2004 at the 200 m and 1000 m water depths represented about 10% and 15%, respectively, of annual deposition from Saharan dust events.

The International Atomic Energy Agency’s Environment Laboratories in Monaco (IAEA, NAEL) are supporting Member States (MSs) in understanding the marine environment by applying isotopic and nuclear techniques. In this context NAEL may take part in scientific cruises with the aim to assist MSs in marine radioactivity monitoring and assessment.

Characterization of atmospheric aerosols collected in Monaco (2004–2008) and in sediment traps at 200 m and 1000 m water depths at the DYFAMED (Dynamics of Atmospheric Fluxes in the Mediterranean Sea) station (2004) was carried out to improve our understanding of the impact of Saharan dust on ground-level air and on the water column. Activity concentrations of natural (210Pb, 210Po, uranium and radium isotopes) and anthropogenic (137Cs, 239Pu, 240Pu, and 239+240Pu) radionuclides and their isotopic ratios confirmed a Saharan impact on the investigated samples. In association with a large particulate matter deposition event in Monaco on 20 February 2004, the 137Cs (∼40 Bq kg−1) and 239+240Pu (∼1 Bq kg−1) activities were almost a factor of two higher than other Saharan deposition dust events. This single-day particle flux represented 72% of the annual atmospheric deposition in Monaco. The annual deposition of Saharan dust on the sea was 232–407 mBq m−2 for 137Cs and 6.8–9.8 mBq m−2 for 239+240Pu and contributed significantly (28–37% for 137Cs and 34–45% for 239+240Pu) to the total annual atmospheric input to the northwest Mediterranean Sea. The 137Cs/239+240Pu activity ratios in dust samples collected during different Saharan dust events confirmed their global fallout origin or mixing with local re-suspended soil particles. In the sediment trap samples the 137Cs activity varied by a factor of two, while the 239+240Pu activity was constant, confirming the different behaviors of Cs (dissolved) and Pu (particle reactive) in the water column. The 137Cs and 239+240Pu activities of sinking particles during the period of the highest mass flux collected in 20 February 2004 at the 200 m and 1000 m water depths represented about 10% and 15%, respectively, of annual deposition from Saharan dust events.

129I, 236U, 239Pu and 240Pu isotopes have been analyzed in the different layers of a peatbog core collected in Madagascar Island (South Hemisphere) and representing at least the last 100 years of atmospheric deposition. The determination of ultra-low levels of these isotopes has been possible by applying the Accelerator Mass Spectrometric Technique (AMS) by using the 1 MV Tandetrom AMS facility located at CNA (Seville, Spain). The elements of interest were extracted and isolated previous to the measurements by applying validated radiochemical procedures. In this contribution, the behavior along the core of the different isotopes under analysis will be discussed, evaluating in particular the magnitude of their post-depositional retention/migration. In this sense, it will be highlighted the great mobility of the 129I with a near uniform profile along the core, in opposition for example with the preservation for the Pu isotopes of the fallout bomb peak. In the case of 236U, the 236U/239Pu atomic ratios determined in a total of eight layers of the core are ranging in the interval 0.02 – 0.29 with an average value of 0.15. As far as we know, these are the first 236U results seeing the light that were obtained in deposits as peatbogs collected in the southern hemisphere.

The preparation and characterization of certified reference materials (CRMs) for radionuclide content in sediments collected offshore of Bikini Atoll (IAEA-410) and in the open northwest Pacific Ocean (IAEA-412) are described and the results of the certification process are presented. The certified radionuclides include: 40K, 210Pb (210Po), 226Ra, 228Ra, 228Th, 232Th, 234U, 238U, 239Pu, 239+240Pu and 241Am for IAEA-410 and 40K, 137Cs, 210Pb (210Po), 226Ra, 228Ra, 228Th, 232Th, 235U, 238U, 239Pu, 240Pu and 239+240Pu for IAEA-412. The CRMs can be used for quality assurance and quality control purposes in the analysis of radionuclides in sediments, for development and validation of analytical methods and for staff training.

The Centro Nacional de Aceleradores (CNA) hosts a 1 MV accelerator mass spectrometry (AMS) apparatus since September 2005. In order to improve its overall performance, several updates have been made on the existing facility during the last 10 years of operation. In this paper, two modifications conducted in 2015 will be described. To increase the transmission of the ions through the accelerator, the stripping gas on the 1 MV CNA machine was changed from Ar to He. The measured maximum transmission for almost every isotope results to be higher, especially for heavy masses: for instance, in the case of uranium in the 3+ charge state, the transmission increased from 11% with Ar gas to about 38% with He gas. The second advance consisted of the substitution of the existing gas ionization chamber with a new one provided by ETH Zurich. The ETH detector features with its miniaturized design and is optimized for low energy AMS (i.e. very low electronic noise and efficient charge collection). As the electronic noise is the most important contribution to the resolution for light ions, the total energy resolution has been reduced by 15% in the case of Be, allowing a better discrimination against its isobar, B. For the heaviest radionuclides where the quality of the spectra is determined by the charge carrier production in the gas, the resolution for 2.7 MeV uranium ions was improved by 30%, probably due to a more efficient charge collection.

In this work, we present first U results in the northwestern Mediterranean. U is studied in a seawater column sampled at DYFAMED (Dynamics of Atmospheric Fluxes in the Mediterranean Sea) station (Ligurian Sea, 43°25'N, 07°52'E). The obtained U/U atom ratios in the dissolved phase, ranging from about 2 × 10 at 100 m depth to about 1.5 × 10 at 2350 m depth, indicate that anthropogenic U dominates the whole seawater column. The corresponding deep-water column inventory (12.6 ng/m or 32.1 × 10 atoms/m) exceeds by a factor of 2.5 the expected one for global fallout at similar latitudes (5 ng/m or 13 × 10 atoms/m), evidencing the influence of local or regional U sources in the western Mediterranean basin. On the other hand, the input of U associated to Saharan dust outbreaks is evaluated. An additional U annual deposition of about 0.2 pg/m based on the study of atmospheric particles collected in Monaco during different Saharan dust intrusions is estimated. The obtained results in the corresponding suspended solids collected at DYFAMED station indicate that about 64% of that U stays in solution in seawater. Overall, this source accounts for about 0.1% of the U inventory excess observed at DYFAMED station. The influence of the so-called Chernobyl fallout and the radioactive effluents produced by the different nuclear installations allocated to the Mediterranean basin, might explain the inventory gap, however, further studies are necessary to come to a conclusion about its origin.

In the last years, 236U (T1/2=2.34·107 y), which is essentially an anthropogenic radionuclide, has been established as a new oceanographic tracer thanks to its conservative behaviour in seawater. At the Centro Nacional de Aceleradores (CNA), in Seville (Spain), it has been recently demonstrated that 236U can be determined at environmental levels on the 1 MV Accelerator Mass Spectrometry (AMS) system. In the framework of the existing collaboration between the National Marine Information and Research Centre (NatMIRC), in Namibia, and the IAEA Environment Laboratories in Monaco, 236U has been analysed by AMS at CNA in a set of seawater samples collected in the northern Benguela upwelling system, on the Namibian coast. In surface samples, 236U/238U atom ratios at the level of 10-10 have been obtained, in agreement with the expected values for the so-called global fallout. The 236U inventories reported up to now in seawater are discussed.

In this paper we present the first comprehensive analysis of the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA, Seville, Spain) for 236U studies in environmental samples. In the last years, this radionuclide has become key in the AMS community, due to the very demanding 236U/238U abundance sensitivities required for general applications. As we demonstrate, the AMS system at the CNA is able to achieve sensitivity for the 236U/238U ratio of about 3 × 10−11 despite its compact design. The use of “239Pu”/238U ratio as a proxy for “236U”/235U background correction is proposed and tested with natural samples that were also studied on the 600 kV Tandy AMS system at the ETH Zürich. This correction is significant in the CNA case, due to the low mass resolving power of the low-energy spectrometer and to the lack of a third filter on the high-energy side. With the measurement of reference solutions supplied by the Institute for Reference Materials and Methods (IRMM-075), and reference natural matrixes provided by the International Atomic Energy Agency (IAEA-Soil-6, IAEA-375; 384; 386 and IAEA-RGU), we show that the 1 MV AMS system at the CNA can be routinely used for determinations of anthropogenic 236U at environmental levels.

After the SNAP 9A satellite accident in 1964, the dispersion of Pu was investigated as a function of latitude North and South. It was obvious that most of the fallout of 238Pu was on the southern hemisphere. However no data from Madagascar, where the accident happened, were reported. This paper describes the analysis of peat bog samples for Pu-isotopes by alpha spectrometry after radiochemical separation. To investigate especially the presence of 239Pu, selected samples were analyzed for 239Pu and 240Pu using mass spectrometric analyses, AMS.

Trabajo presentado a la International Conference on Accelerator Optimization, celebrada en Sevilla (España) del 7 al 9 de octubre de 2015.

SARA (Spanish Accelerator for Radionuclides Analysis) was the first multielemental AMS facility installed in Spain in 2005. Since then it has been dedicated to the routine analysis of several radionuclides, such as 10Be, 14C, 26Al, 129I and Pu isotopes. Tests have been carried out with other isotopes, such as 41Ca, 236U and 237Np, and several changes have been made to the original facility to improve performance. First, an upgraded version of the ion source SO-110 has allowed us more stable measurement conditions for volatile elements (i.e. iodine), and a better general performance. Besides, changes in the target geometry have improved the ionization efficiency and long-term stability of the source output. Moreover, different software upgrades have been introduced to meet our routine operational needs. Finally, changing the movable Faraday-cup associated electronics now allows the measurement of smaller currents (in the range of pA), which has been key for the study of 236U/238U atomic ratio in environmental samples. Apart from these modifications it has to be noted that routine radiocarbon measurements have been moved to a Micadas system (200 kV) installed at CNA in 2012. In this paper we will illustrate the evolution of the facility up to now, and our future prospects will be introduced.

The performance of the 1 MV AMS system at the CNA (Centro Nacional de Aceleradores, Seville, Spain) for 236U and 239,240Pu measurements has been extensively investigated. A very promising 236U/238U abundance sensitivity of about 3 × 10-11 has been recently achieved, and background figures for 239Pu of about 106 atoms were reported in the past. These promising results lead to the use of conventional low energy AMS systems for the analysis of 236U and 239Pu and its further application in environmental studies. First 236U results obtained on our AMS system for marine samples (sediments and water) are presented here. Results of two new IAEA reference materials (IAEA-410 and IAEA-412, marine sediments from Pacific Ocean) are reported. The obtained 236U/239Pu atom ratios, of 0.12 and 0.022, respectively, show a dependency with the contamination source (i.e. local fallout from the US tests performed at the Bikini Atoll and general fallout). The results obtained for a third IAEA reference material (IAEA-381, seawater from the Irish Sea), are also presented. In the following, the uranium and plutonium isotopic compositions obtained on a set of 5 intercomparison seawater samples from the Arctic Ocean provided by the ETH Zürich are discussed. By comparing them with the obtained results on the 600 kV AMS facility Tandy at the ETH Zürich, we demonstrate the solidity of the CNA technique for 236U/238U determinations at, at least, 7 × 10-10 level. Finally, these results are discussed in their environmental context.

A Certified Reference Material (CRM) for radionuclides in seaweed (Fucus vesiculosus) from the Baltic Sea (IAEA-446) is described and the results of the certification process are presented. The 40K, 137Cs, 234U and 239+240Pu radionuclides were certified for this material, and information values for 12 other radionuclides (90Sr, 99Tc, 210Pb (210Po), 226Ra, 228Ra, 228Th, 230Th, 232Th, 235U, 238U, 239Pu and 240Pu) are presented. The CRM can be used for Quality Assurance/Quality Control of analysis of radionuclides in seaweed and other biota samples, as well as for development and validation of analytical methods, and for training purposes.

Radioactive residues, in order to be classified as Low-Level Waste (LLW), need to fulfil certain conditions; the limitation of the maximum activity from long-lived radionuclides is one of these requirements. In order to verify compliance to this limitation, the abundance of these radionuclides in the residue must be determined. However, performing this determination through radiometric methods constitutes a laborious task. In this work, 129I concentrations, 239+240Pu activities, and 240Pu/239Pu ratios are determined in low-level radioactive residues, including resins and dry sludge, from nuclear power plants in Spain. The use of Accelerator Mass Spectrometry (AMS) enables high sensitivities to be achieved, and hence these magnitudes can be re determined with good precision. Results present a high dispersion between the 129I and 239+240Pu activities found in various aliquots of the same sample, which suggests the existence of a mixture of resins with a variety of histories in the same container. As a conclusion, it is shown that activities and isotopic ratios can provide information on the processes that occur in power plants throughout the history of the residues. Furthermore, wipes from the monitoring of surface contamination of the José Cabrera decommissioning process have been analyzed for 129I determination. The wide range of measured activities indicates an effective dispersal of 129I throughout the various locations within a nuclear power plant. Not only could these measurements be employed in the contamination monitoring of the decommissioning process, but also in the modelling of the presence of other iodine isotopes.

As part of the GEOTRACES Program, six laboratories participated in an intercalibration exercise on several anthropogenic radionuclides of interest. The effort was successful for 239,240Pu activity, 240Pu/239Pu isotope ratio, and 137Cs activity measured in filtered seawater samples from the Bermuda Atlantic Time Series station (BATS) and a site on the continental slope of the Northeastern U.S. A limited number of analyses were reported for 237Np, 241Am, 90Sr, and 238Pu in filtered seawater. Intercalibration of any of the isotopes of interest in filtered particulate matter was unsuccessful due to insufficient size of the samples distributed. Methods used were based on traditional radio-counting techniques and inductively coupled plasma mass spectrometry (ICP-MS). Although the majority of analyses were performed on samples ≥ 60 L, one lab demonstrated the ability to analyze several of the anthropogenic radionuclides on 10–20 L sample volumes using ICP-MS.

New analytical methods developed at the facilities here, based on two ultra-sensitive mass spectrometry (MS) techniques, inductively coupled plasma sector field mass spectrometer with a desolvator system (Aridus-ICP-SFMS) and accelerator MS (AMS), have been applied in this work for the reassessment of 239Pu in alpha spectrometry (AS) planchets corresponding to spiked human urine samples. The obtained 239Pu minimum detectable activities (MDAs) values by Aridus-ICP-SFMS and AMS were 3 fg (∼6.92 µBq) and 0.4 fg (∼0.92 µBq), respectively, per sample, which are much better than those attainable by AS [50 fg (∼115.3 µBq) of 239Pu per sample, approximately]. Therefore, it is demonstrated that the MS techniques employed in this work are very powerful tools for internal dosimetry studies in human urine samples, giving excellent results when the reassessment of AS planchets is needed (samples with a Pu concentration below or at the MDA levels measurable by AS). This work is the continuation of an article published in J. Anal. At. Spectrom. 25 (1410–1415) 2010.

Plutonium is present in every environmental compartment, due to a variety of nuclear activities. The Southern Hemisphere has received about 20% of the global 239Pu and 240Pu environmental inventory, with an important contribution of the so-called tropospheric fallout from both the atmospheric nuclear tests performed in the French Polynesia and in Australia by France and United Kingdom, respectively. In this work we provide new data on the impact of these tests to South America through the study of 239Pu and 240Pu in soils from different areas of Northern, Central and Southern Chile. The obtained results point out to the presence of debris from the French tests in the 20–40° Southern latitude range, with 240Pu/239Pu atomic ratios quite heterogeneous and ranging from 0.02 to 0.23. They are significantly different from the expected one for the global fallout in the Southern Hemisphere for the 30–53°S latitude range (0.185 ± 0.047), but they follow the same trend as the reported values by the Department of Energy of United States for other points with similar latitudes. The 239 + 240Pu activity inventories show as well a wider variability range in that latitude range, in agreement with the expected heterogeneity of the contamination.

This work describes two methods for rapid and simple preparation of urine samples for determining the 239Pu content. The preparation of the samples was carried out by evaporation or coprecipitation of Pu, followed by acidic digestion in a microwave oven. The concentration and purification of Pu were achieved by using ion exchange resins AG1X2 and AG1X8 (Bio-Rad Laboratories). The quantification of 239Pu was carried out employing three different instrumental techniques, the more conventional Alpha Spectrometry (AS), and two mass spectrometry methods: High-Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS) and a low-energy Accelerator Mass Spectrometry (AMS). The chemical yield was determined by AS being, on average, 76 ± 7%. The minimum detectable activity (MDA) for AS, HR-ICP-MS and AMS was, respectively, about 50 fg (∼0.1 mBq), 23 fg (∼0.05 mBq) and 0.44 fg (∼1 Bq) per sample, respectively. The results presented in this work demonstrate the excellent performance and suitability of the mass spectrometric techniques for the routine measurement of 239Pu at ultratrace levels in human urine samples, and also for the reassessing of AS planchets if it were needed. The application of HR-ICP-MS and low-energy AMS reduces the sample processing time, and helps us to improve the laboratory productivity, also giving better MDA values when compared to the classical radiometric methods. © 2011 The Royal Society of Chemistry.

In this work we present the most recent improvements performed by our group on 10Be measurements on the 1 MV AMS system recently set up at the CNA (Centro Nacional de Aceleradores), in Seville (Spain). Our efforts have been focused on the study of the viability of our system for BeO and BeF- measurements. To achieve this, different standard materials have been measured to demonstrate the reliability of the system for BeO measurements in a wide 10Be/9Be atomic ratio range and several environmental samples have been studied both at the 1 MV AMS CNA facility and at the 6 MV AMS ETH-PSI facility of Zurich to validate our measurements. The results show a good agreement between laboratories. New experiments also have been carried out selecting 1+ and 2+ charge states at the exit of the accelerator and inserting Si3N3.1 foils with different thicknesses to separate 10Be from its isobar, 10B. The influence of each foil on the overall transmission (detected 10Be compared to BeO- injected into the accelerator) and background level was also assessed. In addition some tests were also done to assess the viability of BeF2 and BaBeF4 measurements at our system. Several metal matrices and cathode preparation procedures for BeO samples were investigated to maximize current and cathode lifetime. © 2009 Elsevier B.V. All rights reserved.

Since the last nuclear atmospheric test carried out by the People Republic of China in 1980 and since the Chernobyl accident in 1986, the plutonium hasn't been directly released into the atmosphere. However, nowadays, it is still present in the troposphere. This is due to plutonium-bearing soil particles physical resuspension processes. In this work, we study for the first time the temporal variation of plutonium isotopes, 239Pu and 240Pu, baseline concentrations on a monthly basis in surface air from Seville (Spain), and their correlation with some tracers of mineral dust, during 2001 and 2002. The Pu analyses were performed by low-energy Accelerator Mass Spectrometry (AMS). The 239Pu plus 240Pu (239+240Pu) activity levels achieved maximums during the summer period, characterized by the absence of rains, and minimums during the rainy seasons, laying in the range 1-20 nBq m-3. The 240Pu/239Pu two-year average atomic ratio was 0.18 ± 0.03, in agreement with the fallout plutonium. A good correlation with Pu and Al and Ti levels is observed. They are crustal components usually used as tracers of African dust over European countries. The hypothesis of the influence of the Saharan dust intrusions is supported as well through the study of Total Ozone Mass Spectrometer (TOMS) daily images. © 2010 Elsevier Ltd.

The measurement of plutonium isotopes, 239Pu and 240Pu, at 670 kV on the compact accelerator mass spectrometry (AMS) system at the Centro Nacional de Aceleradores (CNA) in Seville, Spain, is now a reality. In this work, we present first Pu AMS results for environmental samples: a sediment core collected in a submarine canyon in the Mediterranean coast of the Spanish region of Palomares, affected by a nuclear accident in 1966. From the study of the 240Pu/239Pu atomic ratio profile, showing on average levels lower than 11%, we confirm that the weapon-grade plutonium released on land during the accident, with a characteristic 240Pu/239Pu atomic ratio of 5.8%, has found its way into the marine environment. A two-plutonium sources mixture model (Palomares and fallout) is used to elucidate the percentage of the plutonium coming from the accident. As a validation exercise of the Pu AMS measuring technique and in order to obtain the 238Pu/(239+240)Pu activity ratios, samples were also studied by alpha-spectrometry (AS). The obtained AS 239+240Pu activity concentration results fit in with the AMS ones in a wide dynamic range, thus validating the AMS technique. © 2009 Elsevier B.V. All rights reserved.

Since the 1950s, nuclear weapon testing and releases from the nuclear industry have introduced anthropogenic radionuclides into the sea, and in many instances their ultimate fate are the bottom sediments. The Arctic Ocean is one of the most polluted in this respect, because, in addition to global fallout, it is impacted by regional fallout from nuclear weapon testing, and indirectly by releases from nuclear reprocessing facilities and nuclear accidents. Sea-ice formed in the shallow continental shelves incorporate sediments with variable concentrations of anthropogenic radionuclides that are transported through the Arctic Ocean and are finally released in the melting areas. In this work, we present the results of anthropogenic radionuclide analyses of sea-ice sediments (SIS) collected on five cruises from different Arctic regions and combine them with a database including prior measurements of these radionuclides in SIS. The distribution of 137Cs and 239,240Pu activities and the 240Pu/239Pu atom ratio in SIS showed geographical differences, in agreement with the two main sea ice drift patterns derived from the mean field of sea-ice motion, the Transpolar Drift and Beaufort Gyre, with the Fram Strait as the main ablation area. A direct comparison of data measured in SIS samples against those reported for the potential source regions permits identification of the regions from which sea ice incorporates sediments. The 240Pu/239Pu atom ratio in SIS may be used to discern the origin of sea ice from the Kara-Laptev Sea and the Alaskan shelf. However, if the 240Pu/239Pu atom ratio is similar to global fallout, it does not provide a unique diagnostic indicator of the source area, and in such cases, the source of SIS can be constrained with a combination of the 137Cs and 239,240Pu activities. Therefore, these anthropogenic radionuclides can be used in many instances to determine the geographical source area of sea-ice. © 2010 Elsevier B.V.